![]() ![]() Trigraph replacement: The preprocessor replaces trigraph sequences with the characters they represent.Preprocessing is defined by the first four (of eight) phases of translation specified in the C Standard. ![]() The C preprocessor was part of a long macro-language tradition at Bell Labs, which was started by Douglas Eastwood and Douglas McIlroy in 1959. It was extended shortly after, firstly by Mike Lesk and then by John Reiser, to incorporate macros with arguments and conditional compilation. Its original version offered only file inclusion and simple string replacement using #include and #define for parameterless macros, respectively. The preprocessor was introduced to C around 1973 at the urging of Alan Snyder and also in recognition of the usefulness of the file-inclusion mechanisms available in BCPL and PL/I. The language of preprocessor directives is only weakly related to the grammar of C, and so is sometimes used to process other kinds of text files. In many C implementations, it is a separate program invoked by the compiler as the first part of translation. The preprocessor provides inclusion of header files, macro expansions, conditional compilation, and line control. The C preprocessor is the macro preprocessor for several computer programming languages, such as C, Objective-C, C++, and variety of Fortran languages. ( Learn how and when to remove this template message) ( March 2015) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. This article includes a list of general references, but it lacks sufficient corresponding inline citations.
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